Fast growth of highly ordered porous alumina films based on closed bipolar electrochemistry

Highly ordered porous anodic alumina (PAA) is widely used as a template for preparing one-dimensional nanostructured materials. At present, research efforts to prepare PAA templates with straight channels mainly focus on improving their regularity or increasing the efficiency of the preparation methods. Herein, we introduce a novel anodization method to fabricate highly ordered PAA films based on closed bipolar electrochemistry. To the best of our knowledge, there have been no reports of the use of closed bipolar electrochemistry in PAA film fabrication. Compared to traditional anodization, a faster PAA film growth rate of 1.67 mu m min(-1) was obtained in 0.75 M oxalic acid when a voltage of 62 V was applied to the driving electrodes. Furthermore, different electrolyte solutions can be employed in the anodic and cathodic cells in the closed bipolar electrochemical system. In addition, no direct electrical connection to the aluminum sheets is required in this approach.